Ocean waves are generated in an ocean region by wind acting upon an upper surface of the ocean region. Wind is itself caused by spatial differences in atmospheric temperature as a consequence of solar radiation being absorbed at the Earth. Ocean waves are effectively surface waves which are devoid of any general overall flow of ocean water, but merely an oscillatory motion of water about a mean position. Energy content of ocean waves reduces exponentially with depth from an upper ocean surface at a rate depending upon ocean wave wavelength. In a similar manner to other types of waves, for example electromagnetic waves, ocean waves can be reflected, diffracted, refracted and absorbed.
Renewable energy systems adapted for generating energy from ocean waves have to contend with numerous technical challenges. For example, ocean water is corrosive. Moreover, ocean waves vary greatly in amplitude, wavelength and complexity with time. Ocean wave energy can often be an order of magnitude greater under storm conditions in comparison to normal conditions. Moreover, situations can arise wherein ocean wave energy is negligible. Additionally, designers of ocean wave energy systems have to consider commercial viability of such systems in comparison to alternative systems such as wind turbine power generation systems, hydroelectric power systems, tidal power generation systems, fossil fuel burning power generation systems and nuclear power systems; many renewable energy systems suffer a problem of requiring costly robust structures, for example to withstand storm conditions, whilst generating relatively modest amounts of power when in operation in comparison to a corresponding size of a nuclear power station or fossil fuel power station. Thus, in order to improve commercial viability of ocean wave energy systems, it is highly desirable to ensure that such systems are designed and implemented to exhibit an enhanced operating efficiency for converting energy of ocean waves to electrical energy or similar alternative useful types of energy whilst simultaneously exhibiting sufficient robustness to survive storm conditions.
Many systems have been proposed for extracting useful energy from waves, for example using configurations of floats moving with ocean waves and coupled to pump hydraulic fluids to generate electrical power, ramps for receiving waves with upper overflow ridges for the waves to flow over to be collected to drive a turbine and vertical oscillating columns wherein ocean waves periodically compress air in the columns for actuating an air turbine for generating electricity. In a published Norwegian patent no. NO 327593 attributed to Geir Arne Solheim, there is described an air column 10 disposed in operation at an oblique angle α relative to a general surface plane 20 of an ocean environment 30, as shown in FIG. 1. A first end of the column 10 is arranged to receive waves 40 in operation. A second end of the column 10 is coupled via air valves to an air turbine 50 for generating electricity. The angle α is beneficially in a range of 10° to 35°. Although the air column 10 disposed at the oblique angle α provides a considerable improvement in operating efficiency in comparison to early vertical oscillating air columns for generation of electrical power from ocean waves, it is desirable to improve further operating efficiency of an arrangement as illustrated in FIG. 1 for ensuring its commercial competitiveness against other sources of energy, for example fossil fuels and nuclear power systems.